Motor vehicle steering gear



Sept. 8, 1931. w. N. OSBURN MOTOR VEHICLE STEERING GEAR Filed June I:ll?

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MOTOR VEHICLE STEERING GEAR Filed June 8, 1925 2 Sheets-Shee 2I-IIIlIIII 1 3 m m WXMWW SAL L GHQ: 01 .5

Patented Sept. 8, 1931 UNITED STATES WALLACE N; OSBURN,

OF DETROIT, MICHIGAN, ASSIGNOR TO GEMMER MANUFACTUR- ING COMPANY, ACORPORATION OF MICHIGAN (1925) MOTOR VEHIGLE Application filed June 8,

The invention relates to steering gears and more particularly to theconstruction of gearing between the rotary steering stem and the rockshaft actuated thereby.

construction particularly applicable to high ratio semi-reversiblesteering gears although the construction may also be used with low ratiogears. It is a further object to simplify the construction and to reducethe size of the same without objectionable increase in unit pres sureupon the working surfaces of the gears.

Still further, it is an object to obtain a construction which may beeasily manufactured at a reduced cost.

With this and other objects in view the invention consists in aconstruction as hereinafter set forth.

I In'the drawings:

Figure 1 is a longitudinal section through a steering gear of myimproved construction.

Figure 2 is a horizontal section therethrough in the plane of the rockshaft.

Figure 3 is a plan view of the worm gear. I Figure 4 is a section online 44 of Figure 1 illustrating the worm and gear in intermeshingrelation.

80' In the present state of the art it is usual in steering gears totransmit rotary move,- ment of the steering stem to the rock shaftthrough the medium of an intermeshing worm and segment gear. To make thegear semireversible the helical angle of the worm must be properlyselected to be but slightly outside the angle of friction and this,where a cylindrical worm is used, limits the number of teeth that may besimultaneously in mesh.

Furthermore, with high ratio gears it is necessary that the worm shouldbe capable of revolving through more than one revolution to impart therequired angular movement to the rock shaft. In view of these conditionsI have designed a construction in which the power is normallytransmitted through the engagement of a male thread on the worm with asingle grooved tooth on the worm gear having a line contact therewith.The worm is of a shape such as The object of the invention is to obtaina STEERING GEAR 1925. Serial No. 35,797.

would be generated by said grooved tooth swinging about its normal axisand is prefer-- ably slightly of the Hindley type of hourglass form.However, to secure the necessary angular movement of the gear without.

operation of the steering gear which is through a limited angle ofmovement will be effected solely through the single notched tooth,clearance being provided to avoid other contacts but when the gear ismoved to extreme positions, contact is shifted to its external faces toprovide the required additional movement. v

Viewed in another way, the gear may be regarded as having two teethwhich are alternatively in engagement but these are not developed teethand do not exactly trace the same path of movement.

In detail A is the housing for enclosing the worm B mounted on therotary steering stem C and the worm gear D mounted on the rock shaft E.The worm B is preferably of a length less than the full arc of movementof the worm gear thereby decreasing the size of the houslng which would"otherwise be required. The gear D is provided with a Y-shaped notch Fhaving fiat opposite faces at the desired pressure angles and also at anangle to the plane of rotation corresponding to the desired lead orhelical angle of the thread of theworm. The worm B is such as might begenerated by the notched gear during the rotation of said gear and wormabout their respective axes at uniform velocity. Thus there will be aline contact between the flat face of the gear and the face of the wormin each position of adjustment thereby limiting the unit pressure. Tosimplify the manufacture of the gear D the external surfaces F and F ofthe single notched tooth are formed simultane ously with the oppositefaces of the notch. This may be accomplished by the operation of asingle milling cutter moving through a rectilinear path transverse tothe plane of the gear but nonparallel to the axis of the rock shaft. Theexternal faces F and F are made to clear the face of the thread of theworm when the sides of V-shaped notch F are in contact with the wormthread. This results in the actuation of the gear by a single contactduring the normal operation, the external surfaces F and F coming .intoaction only during the extreme movement and where a limited amount ofback-lash is not objectionable. It also permits of adjustment tocompensate for wear which is greatest in the central .portion of themovement without producing a binding action at the extremes of themovement. Still another advantage is that as the gear moves towards itsextreme position the external faces 1*" and F automatically take up theclearance due to the slight difference in angle from that of a developedtooth face and thus a considerable clearance may be provided between thesaid outer face and the opposed worm faces in the central position ofthe ear.

The construction as above described may be used in any suitableconstruction of steering gear mechanism and in connection withcooperating parts which however, will not be described in detail.

What I claim as my invention is:

1. In a steering gear, the combination with a rotary steering stem and-arock shaft to be actuated thereby, of a gear mounted on said rock shafthaving a single notched tooth, a worm on said stem having a male threadengaging said tooth, and such as would be generated by the simultaneousrotation of said worm and gear about their respective axes, said gearhaving portions on opposite sides of the notch which are in engagementwith the grooves of said worm after disengagement of the male threadfrom said notch.

2. In a steering gear, the combination with a rotary steering stem and arock shaft to be actuated thereby, of a gear mounted on said rock shafthaving a tooth with a V-shaped notch therein, a worm mounted on saidstem having a male thread engaging said V- shaped notch and such aswould be generated by the latter during the simultaneous rotation ofsaid gear and worm about their respective axes, said gear havingportions on opposite sides of said notch normally out of contact withsaid worm but alternatively coming into contact therewith at theopposite end portions of angular movement of said rock shaft.

3. In a steering gear, the combination with a rotary steering stem and arock shaft to be actuated thereby, of a gear mounted on said rock shafthaving a notched tooth, a worm mounted on said stem having a male threadin engagement with the notch of said tooth and such as would begenerated by the latter during the simultaneous rotation of said gearand Worm about their respective axes, said worm being limited in lengthto less than the full arc of movement of said gear and said gear havingportions on opposite sides of said notch normally out of contact withthe worm for engaging and maintaining engagement with the same when saidnotched faces pass beyond engagement.

4. In a steering gear, the combination with a rotary steering stem and arock shaft to be actuated thereby, of a worm and a gear respectivelymounted on said stem and rock shaft having a single loaded toothengagement for a limited angular movement on opposite sides of thecentral position, and an alternative tooth on said gear for maintainingengagement beyond the limits of said central movement.

5. In asteering gear, the combination with a rotary steering stem and arock shaft to be actuated thereby, of a gear having a single notchedtooth forming a pair of projecting teeth on opposite sides of the notchand a worm on said stem having a male thread such as would be generatedby said notched tooth upon the rotation of said gear and worm abouttheir respective axes, the outer faces of said projecting teeth engagingsaid Worm only alternatively and in the outer portions of the angularmovement of said rock shaft.

6. In a steering gear, aworm gear having a single transversely extendingnotch bounded by a pair of projecting teeth, all the surfaces of whichvmay be simultaneously formed by a transverse rectilinear movement of aforming tool, and a worm such as might be generated by the opposedsurfaces of said notch upon the simultaneous rotation of said. gear andWorm about their respective axes,

the outer faces of said pair of teeth engag-,

ing the faces of said worm only alternatively and during the movement ofsaid gear beyond the arc of engagement of said notched surfaces.

7. In a steering gear, a worm gear segment having. a single transverselyextending notch bounded by a pair of projecting teeth all of thesurfaces of which may be simultaneously formed by a transverserectilinear movement,

of a forming tool progressively fed inward into the work and a Worm suchas might be generated by the opposed surfaces of said notch upon thesimultaneous rotation of said gear and worm about their respective axes.

the simultaneous rotation of said gear and worm about their respectiveaxes, the outer faces of said pair of teeth being out of engagement withthe adjacent faces of the worm in the central position of said gearsegment and coming into contact with said faces of the worm alternatelywhen the gear is on one side or the other of its central position.

9. In a steering gear the combination with a rotary steering stem and arock shaft to be actuated thereby, of a gear mounted on said rock shafthaving a notched tooth, a worm mounted on said stem having the malethread in engagement with the notch of said tooth and such as would begenerated by the latter during the simultaneous rotation of said "gearand worm about their respective axes,i said worm being limited in lengthto less than the full arc of movement of said gear and the diameter ofthe outer portions of said worm being also less than twice the radialdistance from the axis of the worm to the ends of the arc of movement ofthe gear, said gear having portions on opposite sides of said notchnormally out of contact with the worm for engaging and maintainingengagement with the same when said notch faces pass beyond engagement.

10. In a steering gear, a Worm and a gear having conjugate toothsurfaces, all of said surfaces of the gear being such as might besimultaneously formed by a transverse rectilinear movement of a formingtool, said movement being non-parallel to the axis of the gear but infixed angular relation thereto and said worm being such as might begenerated by a single opposed pair of said tooth surfaces upon thesimultaneous rotation of said worm and gear about their respective axes.

11. In a steering gear the combination with a rotary steering stem, anda rock shaft to be actuated thereby, of a gear mounted on said rockshaft having a plurality of teeth, a worm on the steering stem such aswould be generated by a single pair of oppositely facing tooth surfacesat the center of said gear dur- .45 ing the simultaneous rotation ofsaid worm and gear about their respective axes, said gear having all ofthe other tooth surfaces thereof clearing the surfaces of the worm whilesaid central pair are in engagement with the worm.

In testimony whereof I afiix my signature.

WALLACE N. OSBURN.

